Rapid and high quality preparation of samples within a histology laboratory, such as tissue sections on a microscope slide, is vital to correctly providing accurate analysis and diagnosis to a patient.
Typically, the workflow within a histology laboratory is as follows:
A biopsy sample is delivered in a container by courier from a doctor's surgery. The sample container is given an accession ID relevant to the laboratory, and is then passed on to the cut-up (grossing) area. Here, the sample is removed from the container, and cut up to excise pieces of interest. The pieces of interest are placed into one or more tissue cassettes, wherein the tissue specimen is held loosely in a cassette to segregate it from other samples. Each cassette is labelled so the tissue can be identified through the entire process. The next step requires the tissue specimen to be processed in a device such as a Leica ASP300. In such processing, the tissue is dehydrated using alcohol, and then infiltrated with paraffin wax to form a chemically stable block. Once stabilised and infiltrated with wax, the tissue is then taken from the cassette and oriented into a position appropriate for sectioning.
The orienting step is done manually and requires skilled operators. It can be time consuming to ensure that the tissue specimen is positioned correctly. This step typically involves taking the specimen out of the cassette, heating it to melt the infiltrated wax, selecting the correct size mould to use, dispensing a small volume of wax to the bottom of the mould, and carefully orientating the tissue specimen. It is critical that the specimen is accurately positioned, as the sectioning of the specimen must be in an appropriate plane to reveal the desired cells. The cassette fixture (holding fixture for the microtome) is then placed on the top of the mould, additional wax is dispensed to embed the fixture to the block and the paraffin block then cooled wherein the wax solidifies. The block is then removed from the mould and ready to be mounted on the microtome to be sectioned. The process, from the time a tissue sample arrives in the laboratory, to the point where a block is mounted on the microtome, adds significant delays to the provision of a diagnosis based on the tissue sample.
In order to decrease the time this process takes, several steps have been automated to various extents. However, other steps, such as the embedding process, have remained manual or semi automatic in a large number of laboratories. The manual embedding process is typically a slow process with an average of 40-60 samples per hour, and has also proven to be very labour intensive requiring the histotechnician to spend a large proportion of time handling individual cassettes. The repetitive nature of this task also exposes histotechnicians to the risk of repetitive strain injuries. Furthermore, as the process involves many manual steps, there is increased risk of errors occurring, such as mixing up tissue identity. Automation of processes in a histology laboratory is seen as beneficial to reducing turn around time, and can be assisted by automatic embedding.
There remains a need for improved methods and devices for automating the embedding process including handling tissue cassettes. The present invention is directed to overcoming or at least alleviating the problems associated with the prior art, or providing a useful alternative.